The research of the Fels Research Institute at Temple University School of Medicine in Philadelphia is divided into three broad areas, the Chemical Carcinogenesis Program, the Cell Biology Program and the Biochemistry Program. The main aim of the Program on Chemical Carcinogenesis is the better understanding, at the molecular and cellular levels, of how certain chemicals cause cancer in animals in vivo and induce malignant transformation of cells in vitro. Investigation is on a broad front using carcinogenic nitrosamines and other N-nitroso compounds, as well as other chemical carcinogens in the study of their distribution in the body, metabolic activation and deactivation, interaction with nucleic acids and proteins, DNA repair mechanisms and morphological studies of tumor development and tumor modification in vivo and in vitro. Members of the Cell Biology Program study, at the molecular and cellular level, the genes and gene products that control cell growth and cell death in neoplastic and normal cells. Areas of study include regulation of the cell cycle by oncoviral antigens, growth factors, genes involved in hybrid cells, effects of chemical and viral carcinogens on human lymphoblastoid cell lines and biochemical mechanisms of cell death. The Biochemistry Program is concerned mainly with biologically active proteins. Areas under investigation include metabolite and steroid binding proteins including ligandin, modification of proteins by protein methylases, including membrane proteins and specific catalytic sites of proteins and relationships between isoenzymes in adult, fetal and tumor tissues.